Diode pumped lasers have grown in usefulness, particularly in industrial, medical and military applications. Diode pumped lasers are particularly useful, because diode pumps are power efficient, all solid-state and long lived. These result in laser systems that are lighter, more efficient and typically not water cooled, as compared to similar flash lamp pumped solid-state lasers.
In general, end-pumped or side pumped solid-state laser configurations are known. Q-switched lasers or monolithic lasers are configurations such as those described in U.S. Pat. Nos. 5,394,413; 5,381,431; 5,495,494; 5,651,023 and 6,373,864 B1. Disadvantages of such designs are, inter alia, limitations regarding the maximal pulse energy. In addition Q-switched lasers are able to only produce pulses of very short duration.
U.S. Pat. Nos. 6,219,361 B1 and 6,377,593 B1 describe side pumped designs, where the beam path takes an internal zig-zag path, such design lengthening the pulse duration and increases manufacturing difficulty and cost.
In diode side-pumped geometries, the gain media is typically either a rod or a slab. Slab geometries have typically been used in conductively cooled laser systems with one side of the slab attached to a thermal heat sink, and with the opposing face used for the introduction of pump light. Side pumped slabs can employ various techniques such as utilizing a so called “zig-zag” optical path, as for example disclosed in US 2007/0060917, FIG. 2b. Zig-zag slabs, however, are difficult to fabricate owing to tight optical tolerances and are therefore more difficult to produce in large quantities than straight through slab embodiments, and are therefore more expensive to produce.
Document WO2004/034523 discloses a monolithic, side pumped, passively Q-switched and not water cooled solid-state laser that includes a laser resonator structure, and that includes a laser gain medium having an output face bonded to a passive Q-switch. The gain medium has a side face for receiving pump light. The pump light is generated by a diode laser array. One disadvantage of this solid-state laser is that the average power is limited. Another disadvantage of this solid-state laser is that thermal effects arise during operation. In addition Q-switched lasers are able to only produce pulses of very short duration.
Document US 2007/0060917 discloses in FIGS. 1b and 2a a MIR (mid-infrared) diode side pumped solid-state laser that includes a laser resonator structure were gain switched pulse can be emitted (FIG. 5c). One disadvantage of this solid-state laser is that the power of the generated laser light is limited and low.
Document U.S. Pat. No. 6,366,596 B1 discloses a diode side pumped OPO laser that generates, inter alia, MIR (mid-infrared) radiation. Although the wavelength can be tuned in a wide range in the MIR wavelength region, the disadvantage of such lasers is the short pulse duration in the one and two digit nanosecond region with high power densities (intensities) or if the laser pulse lengths are in the microsecond region the laser pulse intensity is very low. In addition such lasers are complex, require optical elements with various optical coatings, and are thus very expensive. Another disadvantage is that such lasers are not robust against shock and vibration, and that the large number of critical components increases the likelihood of a system failure.
Documents U.S. Pat. No. 5,642,370; U.S. Pat. No. 5,643,252; U.S. Pat. No. 5,868,731; U.S. Pat. No. 5,908,416; U.S. Pat. No. 5,947,957; U.S. Pat. No. 6,251,102 B1 and U.S. Pat. No. 6,395,000 B1 disclose side pumped solid-state lasers working in the mid-infrared wavelength region. In general such solid-state lasers are used for biological tissue ablation. Some of these lasers are battery powered and so called self contained, delivering single laser pulses followed by a few seconds charge time of the capacitors in the high voltage power supply.
It is therefore an object of the present invention to provide a side-pumped solid-state laser device for generating high power laser light pulses. It is a further object of the present invention to provide an inexpensive, robust and reliable laser device. It is a further object of the present invention to provide a high performance operating laser device, in particular to provide laser light having high pulse energy and/or high power and in particular allowing high pulse repetition rate in a broad working range. It is a further object of the present invention to provide a laser device suitable to be used in the medical field, in particular with a wavelength in the mid-infrared (MIR) range of between 1700 nm to 3200 nm, and/or in particular suitable for treating, cutting or ablating biological tissue. It is a further objective of the invention to provide a treatment device that enables a user to perform high powered laser pulse treatments, where the treatment device is easy to handle, especially a maintenance friendly embodiment should be achieved. Furthermore it is an objective to find a treatment device that allows a high powered laser pulse treatment off site a specialised treatment unit.